For colleges and universities, the Committee on Professional Training of the American Chemical Society states in the 2008 Guidelines that "The number of students supervised by a faculty member or a by a teaching assistant should not exceed 25."  This is non-regulatory, but could be considered "good practice". 

The same limit (24 students) is recommended in this 2012 ACS booklet on page 14:

http://www.acs.org/content/dam/acsorg/education/policies/recommendations-for-the-teaching-of-high-school-chemistry.pdf   Again, good practice, not regulations.

The only caveat worth noting about "good practice" parallels the idea of "standard of care" in the medical field.  If something goes wrong, and a lawsuit ensues, one would not like to defend why "we were not following �good practice' as defined in the field."  Perhaps this can used to help convince those with the authority to adjust lab sizes to consider the possible future effects (risks) of >24 students.   Likely, financial concerns drive these decisions that allow >24, but as with so many decisions one must weigh the cost of "large labs" with the possible cost of some future lawsuit.  (This ignores the "cost" to injured persons, of course - which could be permanent damage or death.)

I am unaware of any state or national regulations about lab size; perhaps others will know better.

Dave

Last year or so there was discussion about class sizes for chemistry lab classes. Are those sizes mandated by a regulatory agency or suggested by a non regulating organization. The specific problem I need to address is potential overcrowding in high school labs designed for 24 students. Current attitudes in education are financily driven not safety driven.
Sent from my U.S. Cellular� Android-powered device